Pressure ratio sensing, indicating, and controlling apparatus



Jan. 31, 1961 w. E. REED 2,969,640

PRESSURE RATIO SENSING, INDICATING, AND CONTROLLING APPARATUS Filed Aug. 25. 1953 5 Sheets-Sheet l1 @ff/M ATTORNEYS 5 Sheets-Sheet 2 W. E. REED :illilllllldh 4,. m y All?. .n 4 m W., M ,J m W m M f-0[ 7m. 1 Xi .l Z @,mt 7. u 1` l nv l?. l.. fb. HA o 4 N, .w 0, m 1 /4 A f 6g L Y A Uli., L f 2 m R Il o s Z 1| s 4. |l 4.. HH- w w 4 2 8 l o k m 6 1 w a e 5 2.

Jan. 3l, 1961 PRESSURE RATIO SENSING, INDICATING, AND CoNTRoLLING APPARATUS Filed Aug. 25. 1953 WENDELL E. REED BY mali M 0% A RNEYS v Jan. 3l, 1961 w. E. REED 2,969,640

PRESSURE RATIO SENSING, INDICATING, AND CONTROLLING APPARATUS y Filed Aug. 25, 1953 5 Sheets-,Sheet 3 m 245 l 1 ZOO l ze 2442` 225 224 I' Z'Z Z9Z 49o 49g 218 244 Z50 284 ZO f u 328 l 234 27e 1o 53o 5, L- l 3io 31g INVENTOR Warum-:LL E. Raab 299 ATTORNEYS Jah- 31, 1951 w. E. REED 2,969,640

PRESSURE RATIO SENSING, INDICATING, AND CONTROLLING APPARATUS Filed Aug. 25. 1953 l5 Sheets-Sheet 4 272 336 27o 278 X V' 638 l 316 330 V INVENTOR. WENDELL E. REED AT TO RN EYS Jan. 31, 1961 w. E. REED 2,969,640

PRESSURE RATIO sENsING, INDICATING, AND coNTRoLLING APPARATUS Filed Aug. 25. 1953 5 Sheets-Sheet 5 360 INVENToR.

WENDELL E. REED ATTORNEYS nite Stats PRESSURElumov SEN-SING, lNnIcAr-nso, AND coNTRoLLnsG. APPARATUS-- This yinyention:relatcsrto: sensing. indicati-ngfandf coni trol yapparatus foruse in -conjunctionfwithtiiuid owssysf tems and more-particularly tofoWindicat-ingand con,- trol devices;v which, are responsive to lvariations in.; the properties t and characteristics ofuidsgiiowingim such; systems as gas turbines.,` reactionengines; chemical,A procs essing apparatus, pipe-lines,- windgtunnels--and-:thc like.

This. application is, a conti-nuationn-part fogcopending application Serial No. l40,856,%now Patent- No.2,746,f 2 42, which discloses-and;claimsfonefformofftheinvention `which isparticularly` useful infconnection vwithythe control of turbo-jet engines, especially thosefequipped with aiterburnera TheA additional formof@ the invention `disclosedin the present application is `of.,moregeneral utilityL- principally because of its greater sensitivity and-:reliability andi-.because of the fact that its performance..issubstantially unaffected byvariationsin environmental conditions;

To indicatethe. versatility of, the apparatust ofE the present invention, it.wi1l, be disclosed: in.. severalA .widely varying. environments, yin ieach oflwhichitfhas produced i results1 heretoforevunobtainable.. Specifically, the. inventiony will bek disclosed as Aa., jet engine. control,- asl.a,flw ratiocontrobandasa remotetemperature control;4 From these widely varying applications otheruses.. and, applications will be suggested.

Atv present tl-iev invention has. achieved .its most. vnotable success lin the iield of 'jetengine control.

As is Well known inthe art, successful methods -.-and apparatus have been developed to augment themass and velocity of the exhaust gases of conventional jetfengines to increase their' thrust by 'injecting andlbfurning additional combustible elements in theunburnedexh'aust gasvcomponents b'yrneans of'an afterburner. Such' after? burners, which are generallyl used only during' take-olf or during unusual flight conditions, produce',.in a frac# tion of asecond,` temperature and pressure variations in Ithe engine, which,` if'not immediatelyrcompensated for, may either destroy or seriously damage the engine or produce a lfatal `loss`of 'thrusts For example, if' an afterburner is switched on duringl normal Hight it increases the output flow' of' exhaust gases from about 2250c.f.`s. to 4200 c.f.s. in'thefraction of a second requiredy for ignition; Compensation for this large -andrapid increasey in the mass of the exhaust' gaseslis accomplished by enlarging they tail pipe nozzle; Conversely, if the'afterburnerisswitchedfoff or blownxout, an immediate-reductionin'tiie mass of-`th'e exhaustugases-'occursf which; if not promptly compensated forA by therreduction of' nozzlefarea produces a' lo'ssof thrustV which may endanger the air craft. Immediate correction of. the nozzle area is critical, for aY singleer roneous or delayed operation .may result in the loss of arplane and its occupants.

For safe .and elicient operation either 'dur-ing.- afterburning or non-afterburning. conditions therturbine `discharge temperature should be maintained. at. a. substan: tially constant maximum and the turbinedischarge presi'atcnt" sureshould be'maintained at a balanced cycle condition, Whichexists duringoperation at'sea level with no afterburning and: with the aircraft at rest and the variable nozzle at minimum opening or with afterburning and the variable nozzle. set at maximum opening. This normal discharge pressure. whichA is determined'. principally by r.p,.m:f, .air aspeedzambient tempera-ture; and compressor eiciency, is found: at; any-altitude of` operation atthe entrance to the tail pipe of a turbo-jet powen'plant1un.- der th'e above stated conditions.

Unavoidable variatonsqin fuel flow and rother factors cause the turbine dischargepressure to depart from normal either during aftcrburning or non-afterburning conditions and such variation, if exceeding a permissible limit, are compensated'for by trimming'the variable area nozzle.

It will be appreciated that the pressure level of the operating cycle of a turbo-jet engine is considerably lower at altitude than at sea level. For example, at full military r.p.m. at sea level, a specific jet engine has a compressor discharge pressure of 93.8 p.s.i.a. and a turbine discharge pressure of 35.2 p.s.i.a. At full military r.p.m. the-same-engine at fifty-five thousandv feet has a compressor discharge pressure of l6;p.s.i.a. and a turbine discharge pressure of.6. p.s.i.a..

It has been found. that the variations in tail-pipe pressure occasioned by afterburner light-off orblow-out are a substantially constant percentage oftheftail-ppe. absolute pressure. at a given altitude and the absolute pressure changes.V accordingly vary widely with altitude. This fact is chie'y responsible for. the failureof the many prior pressure responsive control devices, and. systems which are sensitive onlyY to absolutepressure variations of'a given magnitude. It isQfrthis reason that thecontrol apparatus shown rin the aforesaid. Patent. No. 2,746,- 242 which was the most eiective pressureA controlidevice known prior to the improvedform offth'einvention herein, disclosed has an operational ceiling, of' about 40,000 feet'.

It is" essential in control apparatus of this kind that a dead band area vbe provided to prevent response of the controll apparatus-to the continual minor and insignificant variations in turbine discharge .pressuresto prevent undesirable intermittent opening and closing of the variable nozzle: Such;permssiblervariations in the absoluteture bine discharge pressurealso decrease significantly with altitude'.y However, the'percentage variation' remains sub'- stantially constant.

For example a variation of l to 2%y from/the predetermined'normal turbine discharge pressure is permissible atall'altitudes.y If the control device has a dea'd' band of approximately l.`5 `p.s.i.a. atsea 'le'velVv the absolute pressure increase of 9 `p.s.i.a. at afterburner light-oit and the decrease-of'S p.s.i.a V at blow-'out willV activate the control apparatus and ettect'therequired nozzle adjustment; However, at 40,000' feety thev turbine' discharge pressureincreases zonly 17.95 p.s.\i.a. at-'light-'ofand decreases only "1.5 atfblow-outfofthe.afterburner. Accord ngly, at'altitudes in excess of40,000 feet, the pressure changes f produced by afterburner light-off or blow-out either :fall ,withinrthe deadband of all vknown prior'pressure responsive vnozzle control 'devices orfarectoosmall to aiordthefdesired controlresponse;r Theoperational ceiling of such devices. can be :increasedto someextent only by decreasing thesealevelfdead band which renders the system susceptible'of inadvertent 'operation dueto transient permissibley tail pipe pressure variations.

PriorV proposed temperature Y responsive. devices-r have been far too sluggish and uncertain to follow rapidly changingoperational' conditions.` and tosprovidetheypracticallyr instantaneous response.: required toprotectI the aircraft.,

Patented Jan. 3l, 1961 The present invention and particularly the preferred embodiment, overcomes the foregoing disadvantages of the prior efforts and failures to solve the jet power plant afterburner signalling and control problems by utilizing a novel method and apparatus for producing a sustained reference pressure equivalent to, or bearing a predetermined relation to, the normal turbine discharge pressures during the widely varying operating conditions met by such power plants, and using the dilerential between the reference pressure and the actual turbine discharge pressure to operate any desired type of signalling or control mechanism.

In its preferred embodiment the invention consists essentially of a flow box or device having two orifices in series, the downstream orice being controlled as a function of a differential pressure applied to a pressure responsive member. In another of its forms the invention comprises a flow box or device having exit and entrance orifices which are fixed in operation.

In either'of its primary forms the sensing and control unit of the present invention forms a duct which is the analogue of another duct which may be a part of the system to be controlled or an independent duct associated with the system to be controlled.

The preferred form of the invention eliminates springs and other resilient devices which have limited the range of elective operation of prior devices and it is substantially independent of changing pressure levels in operating uids and ambient surrounding atmosphere. For these reasons and others, including its sensitivity and speed of response it is ideally suited for the sensing and control of other iiuid systems as will more fully appear hereinafter.

it is, accordingly, the primary purpose and object of the present invention to provide novel pressure responsive control systems, methods and apparatus.

It is also an object of the invention to provide novel sensing and control devices operable solely in response to variations in pressure from a prescribed normal.

It is a further object of the present invention to provide novel pressure responsive control units of small size and light weight which substantially completely eliminate mechanical resiliency and which are unaected by changes in ambient pressure levels to provide a uniform response at all altitudes at which turbo-jet engines are able to function efficiently.

It is an additional object of the present invention to provide novel pressure control units capable of sensing small variations between the ratios of a reference pressure and one or more operating pressures or between a reference pressure, one or more operating pressures and ambient pressure.

It is a further and more specific object to provide a novel pressure sensitive control device which when applied to jet engine control systems provides a control signal the magnitude of which is a direct function of the error in jet engine turbine pressure ratio above or below the desired balanced cycle ratio.

It is also an important object of the present invention to provide novel compact pressure sensitive control units which are substantially insensitive to acceleration forces, vibration, temperature gradients andother operating conditions such as those encountered, for example, on an aircraft at all stages of operation from static sea level to supersonic speeds at altitudes in excess of 60,000 feet.

It is a further object of the present invention to provide novel pressure responsive control devices which are capable of controlling the iiow of operating fluids to maintain a predetermined constant pressure ratio between points in the uid system despite wide variations in ambient pressures or in the pressure level of the operating cycle.

It is another object of the present invention to provide novel pressure sensing, indicating and control devices which have a substantially constant Sensitivity Vahle,

which are substantially free from inertia elects and spring and friction losses and which are capable of practically instantaneous action when actuated by pressure variations of a predertermined percentage. t

It is an additional object of the present invention to provide novel pressure responsive control devices which are self-compensating under all conditions and provide a substantially constant sensitivity value despite sudden and major variations in pressures to which they are subjected.

It is another object of the invention to provide novel control systems which are self-balancing, thus eliminating hunting and pendulum action.

It is also an object of the present invention to provide novel control devices and systems which are responsive to constant percentage variations from a predetermined pressure norm.

It is a further object of the present invention to provide novel control devices and systems for controlling a variable jet nozzle associated with a turbo-jet power plant over a wide range of operating conditions.

It is also an object of the present invention to provide novel pressure responsive control units which are compact, inexpensive, lightweight, simple and dependable.

It is a more specific object to provide improved jet engine control units which may be installed on existing equipment with a minimum of modification.

Other objects will become apparent as the description proceeds in connection with the accompanying drawings in which:

Figure l is a schematic diagram of a conventional turbo-jet engine equipped with an afterburner and with a sensing system in accordance with one form of the invention and a fuel control system for the primary burner and afterburner;

Figure 2 is a sectional view of one of the elements of the sensing system shown schematically in Figure l;

Figure 3 is a view similar to Figure 1 illustrating the preferred form of the invention as applied to a jet engine equipped with an afterburner and a fully variable nozzle; v Figure 4 is an enlarged vertical section of the preferred form of the control unit of the present invention taken along line 4 4 of Figure 3;

Figures 5 and 6 are enlarged sectional views taken along lines 5-5 and 6 6 of Figure 4 illustrating details of construction;

Figure 7 is an enlarged sectional view taken along line 7--7 of Figure 6;

, Figure 8 is an enlarged section taken along line 8-8 of Figure 5;

Figures 9 and 10 are schematic wiring diagrams illus trating, respectively, a typical circuit for controlling twoposition and continuously variable area jet nozzles;

Figure 11 is a schematic illustration of the invention utilized as a remote temperature control; and

Figures 12 and 13 are schematic views of the present invention utilized as a flow ratio control device.

Figure l shows schematically a turbo-jet engine of conventional type, having a compressor 10, a primary burner 12, a turbine 14, and an afterburner 16, located in a tailpipe 17. The outlet nozzle 18 of the tailpipe is of such diameter as to handle all of the exhaust gases when both the turbo-jet engine and the afterburner are in operation without increasing the normal discharge pressure. The primary burner may operate with or without the afterburner, but the afterburner is never operated alone. To provide proper tailpipe or nozzle areas a pair of gates 19 and 20 are pivotally mounted upon the tailpipe at 22 and so arranged that when they fully open during afterburning the full discharge area of the nozzle 13 is open and when they are closed the remaining effective area is that required to maintain a normal turbine discharge pressure when the afterburner is not in operation.

The gates 19 and 20 are operated through a linkage system 24 by a fluid motor 25- which is connected to a four'way iluid valve 263 that delivers llnid= to the right end of the motor 25to open thegates, or tothe 'left end ofthe motor to close the gates. Fluid", under pressure issuppliedby line 27, and fluid discharged' from the inactive endv of motor 25? is directedr by the valve 26" to the exhaust line 28; v

In the turbo-jet engine itselfl'the compressor includes stationary blade or nozzle rings, 30 which cooperate with rotating., blade rings 32'mountedupon a driven shaft34 to compress the air enteringV at 35 and to deliver it to the compressor outlet passage 36;.

The compressed air then enters the, primary burner 12 where it i's mixed with fuel' ignited' by spark plugs37, burned', and the products of combustion deliveredto the turbine 14through` guidevanes 38, andthenceto turbine blades 39`ixedly mounted' upon shaft34to supply/.power thereto to* rotate it and djrive the4 air compressor 10i Spark plugs 37 may be energized' by any suitable method which closes switch 40 so that current p asses through spark coi-l 41 to plug 37, and needr remain energized only long enough to initiate burning after which switch 40 is opened deenergizing plugs 37.

Leaving turbine 1'4, the gases enter a turbine discharge passage. 42 in theupstream end of the tailpipeor diffuser 17. Thence the gases pass through the .afterburner 16 and out the tailpipe through the nozzle 18;

Tok place the afterburner 16 in operation throttle 43; Figure 1, isV moved in the plusdirection toits full open position which will cause movable Contact 44 and fixed contact 45 to be closed. Closing contacts 4.4" and,45 causes current from a suitable source as battery 46`t0 ow through conductor 47 which supplies current simultaneously to pump motor 48,` solenoid coifl 49 andjgni- 'tion plug 50,` the current to plug 50` passing through normally closed contacts52 and 53 conductor 54 and spark coil 55'. Pump motor 48 drivesvr the rotary gear PJ-lmp 55.6; connected. at its intake side by conduit, 57n to a, fuel supply, not shown,` and connected at its discharge side to, conduit 58' leadingto afterburner 16'. A conventional relief valve 59 is connected between intake conduit 5.7.and discharge conduit` 58. Also mounted'inconduit 58' are 'the three control valves 60, 62 and 64. Valve 60 is a two-position shut-off valve whichv will be opened as soon as solenoid coil 49 is energized upon closing contacts 44' and 45, and'closed upon deenergization of coil 49. Valves 62 and, 64 are provided to control the amount of fuel pumped to afterburner 16 and are responsivey to variation in pressure rise across compressor 10' and temperature immediately down stream of turbine 114, respectively.

The control element, not shown, of valve 62 isrsecured to an arm 65 which is loosely xed at its, lower end to a rod 66 extending into an airtight cylinder 67. Within the cylinder 67 rod 66 vis secured to a spring biased piston 68 forming one end of a bellows 69. The other end of bellows 69 is formed by the end 70 of cylinder 67. Piston 68 .is exposed on its bellows side to in let or rarn air pressure entering the bellows through line 72, and on its free side to compressor outlet pressure through line 74 so that -any relative change in pressure across compressor 10,'will be reflected by movement of piston 68 andthe control element of valvey 62. Asshown by the arrow, valve `62 will move in a plus or fuel increasing direction in response to an increase in pressure rise across compressor 10. Valve 62 varies the primary control of the fuel supply to the afterburner, the regulationbeing a function of altitude, engine r.p.m. and air speed.

Valve 64 is controlled by thermocouples 75 and 76 or other thermally responsive devices immediately downstream of turbine 14. As is well-known in the art, thermocouples produce a millivolt D.C. power which varies in accordance with the temperature changes of their environment; Thermocouples 75` and 76 are connected .to conductors 77 and 78. Conductor 78leads directly into a conventional amplifier-converter 79 of a type similar to that disclosed in UnitedStates Patent` No. 2,'368g701to. Borden which is supplied by an A.C'.,source, while conductor 77 vpasses through the potentiometer 80 before it' leads to amplifier-converter `79 as isr conventional' in such temperatureindicating and control circuits. The amplifier-converter 79 suppliesy power proportional to the signal received from -thermocouples-f75 and 76 to a reversible variablefspeed motor 81N of anyA suitable type which is connected to valve- 64 through drive shaft 82'. This temperature responsive controly is arranged to operate valve 64 in a fuel decreasing or minus'direction in responseto anl increaseI in the temperature inthe turbine discharge region; Ther primary function of'L the thermocouples'and the thermocouple controlled valve isto allow the aterburner to heat to the greatest degree possible connnensurate-with safev temperatureswithin the metals, Becausev the thermoco/uples are astemperature-sensitive devicethey make; itpossible to use top temperatures' in f the finalf degree of afterburningV which areI somewhat hotter than would be possible relying solely on the more rapidv but less sensitive signals ofthe pressure system.

As explained 'hereinbefore the closing of contacts 44 and 45 send current to ignition plug 50 which will ignite the fuel being introduced into the diffuser 17 just upstreaml of afterburner 16 asA shown at 84 to start the afterburning. Since the plug 50 need be energized only long enough yto start the afterburningthe contacts 52 and 53 are opened when gates 19 and 20 are in their fully open position in any suitable manner," for example as shown diagrammatically by a gate in dotted lines in F-figu're l, and as will bev morev fullyexplained hereina ter.

Fuel is supplied to the primary burner from the fuel supply, not shown, by means of rotary'gear pump 85 driven by vmain engine shaft 34. Fuel enters the pump through conduit- 86 and is discharged into conduit 87 which connects with an annular conduit 83 and the fuel injection nozzles S9 for the primary burner, all of which are conventional. A relief valve of any suit,- able design connects conduits 86 andv 87 on either side of pump 85. Also xed in the conduit 87 are the fuel control valves 92 and 94. Valve 92 is controlled by' a fly-ball governor 95V mountedon shaft 3K4 with its inner end'xedto the shaft and its outer end slidable on the shaft. A suitable linkage, such for-example as diagrammatically illustratedl by: arm 96, armv 97 and arm 98 pivoted` at 99, transmitsthe movement ofthe outer end of governorv 95 to the control element, not shown, of valve 92. An increasein the speed of rotation of shaft '34 will'cause valve 92 to be moved in a minus or fuel decreasing direction. Valve 94 is controlled by the throttle 43 through a linkage such asv levers 100 and 102, and any movement'of the throttle 43 in either direction is transmitted directly to valve 94. It should be noted that the primary control offuel to the primary burner is achieved by throttle controlled valve 94, the governorvcontrolled valve 92 serving only to maintain turbine speed below some predetermined permissible maximum.

vWith the afterburner 16 not in operation gates 19 and 20 are closed, as shown, and the outlet passage from nozzle 18 is thereby reduced to its smallest opening; Whenfthe afterburner is placed in operationy it adds addif tional fuel to the exhaustv gases (which have a surplus of air in turbojet engines) andthe mixture is largely burned before it discharges through thel nozzle 1:8, thereby increasing the temperature and` hence the volume of the exhaust gases. If the discharge pressure is allowed; to increase over a normal value, the turbine will be slowed, the speed responsive governor 95'Wi1l supply more fuel,'and the temperatures resulting from theburning gases in the` primary burner 12 may reach destructive levels. To maintainv a normal turbine discharge pressure after the afterburner has been placed in operation the nozzle 18 must immediately be enlarged by opening gates 19 and 20. For that reason I control variation of the size of nozzle 18 in novel manner by means of a reference pressure which constantly simulates the previously defined normal turbine discharge pressure. Accordingly, in my invention actual control of the nozzle opening is dependent upon the difference between the said normal turbine discharge pressure (as represented by the pressure in chamber or cavity 105, as will be described) and the actual turbine discharge pressure for any operating condition.

Referring again to Figure 1, at 104 the instrument shown in detailed construction in Figure 2, which may be aptly described as a variable comparison pressure device, is schematically illustrated. The body of the pressure device 104 has a central chamber or cavity 105 which is connected to a pipe 106 via an orifice 107 which may have a removable filter screen 108 attached to a flange 109 held in place as by pipe 106. The pipe 106 is connected to the engine so as to have its inlet subject to the static pressure of the air at the compressor outlet passage 36. It is subjected to the pressure at this point rather than that at the turbine inlet and immediately downstream of the combustors because the gas temperatures reaching the turbine inlet may be 1200 F. or higher and may include sundry solid particles of combustion which tend to deposit in the pipe 106 and the filter screen 108. The static pressure in the compressor outlet passage 36 will be higher than the ambient pressure. The central cavity 105 of the pressure device 104 besides being connected to the pipe 106 is provided with a second orice 110 the area of which is controlled by a needle valve 112. Orifice 110 connects with a pasascenso sageway 114 which is in direct communication with a zone of ambient atmospheric pressure in such manner that the pressure in passageway 114 will be maintained substantially at ambient air pressure. Air will therefore fiow through pipe 106 and orifice 107 into the cavity 105, and then through orifice 110 to the atmosphere. A feature of this cavity is that the orifices are not in line so that the orifice 110 will not be affected by the velocity head occasioned by flow through orifice 107.

The needle valve 112 is so adjusted with respect to orifice 110, and both orifices 107 and 110 are of such diameter and configuration that the pressure drop through the orifice 107 closely approximates the pressure drop through the turbine 14. The pressure drop through the orifice 110 closely approximates the pressure drop through the tailpipe 17 when the afterburner 16 is not operating and the area of nozzle 18 is smallest by reason of gates 19 and 20 being closed. Figure 2, hereinafter described in detail, shows by way of example a scale section through an actual device found practical in one application of the invention.

Pressure drop through the primary burner 12 is balanced out closely by subjecting the inlet of pipe 106 solely to static pressure at the compressor discharge rather than to combined static and velocity head at the inlet to the turbine 14. As a consequence, the pressure in the cavity 105 of the pressure device 104 is the equivalent for any operating condition, of the normal turbine discharge pressure.

In the schematic diagram of Figure l a pair of resilient bellows or Sylphons or the like are diagrammatically indicated at 115 and 116, with their outer ends fixed to a. suitable frame 117 and their inner facing ends rigidly connected to a T-shaped element 118. The bellows 115 is connected to a pipe 119 which connects the interior of the bellows with cavity 105. The interior of bellows 116 is connected to a pipe 120 having at its other end an open entrance facing upstream at 122 in the tailpipe 17 at the turbine discharge, so that the interior of the bellows 116 is subjected to the combined static and velocity head of the exhaust gases from the turbine. The bellows or Sylphons 115 and 116 are resiliently balanced 8 so that when the internal pressure within them is equal they will assume a zero or neutral position. l

Also mounted upon the frame 117 are a pair of electrical contacts 124 and 125 on opposite sides of a central contact 126that is carried by the depending leg of the T-shaped element 118. The contacts 124 and 125 are so located with respect to the contact 126 that they are equally spaced therefrom when the bellows and 116 are in neutral position, and so that either one or the other will be engaged by the movable contact 126 when a differential of the pressures in bellows 115 and 116 causes a shifting of the element 118. The contacts 124, and 126 form part of an electric circuit which includes a batery or source of 127, wires 128, 129 and 130, and a motor 132 that drives the valve 26 in either direction to open or close the gates 19 and 20, depending on whether the central contact engages contact 124 or 125. The battery 127 will be in the circuit to drive the motor irrespective of Whether the central contact 126 engages contact 124 or 125.

The illustrated pressure device 104 and `orifices are believed to give a sufficiently close approximation to be suitable for any of the known aircraft jet engines and it is well within the scope of aerodynamicists to design orifices suitable to simulate the pressure drop through any other engine and tail pipe where such a reference pressure is desired for the control of a nozzle control of fuel or for any other indication or control purpose.

Figure 2 shows to scale a section through a pressure device that is operative in the desired manner. The body of the pressure device has its orifice 107 in direct alignment with the pipe 106 that leads to the compressor discharge pressure. The walls of the orifice 107 are rounded on the high pressure side, as are the walls of the orifice 110 on irts side facing the cavity 105. In this example orifice 107 is 0.116 inch diameter and orifice 110 is 0.185 inch diameter, and the rounded high pressure sides of both orifices have radii of roughly 0.094 inch to give the desired ow characteristics or more specifically to simulate pressure drops through turbine 14. Passageway 114 which is connected to a zone of ambient pressure is threaded to receive a conduit 134 that leads to such a zone. The connection between pipe 119 and the cavity 105 is show-n perpendicular to the plane of the drawing. Two other openings to the cavity 105, for such use as may be needed, are shown closed by threaded plugs and 136.

In practice it is desirable to have an adjustment for either orifice 107 or 110. Needle valve 112 which adjusts the discharge to ambient atmosphere through orice 110 has a screwdriver slot 137 and is locked in adjusted position by a pair of nuts 138. After initial adjustment of orifice 110 has once been made for a particular power plant unit the cavity 105 will thereafter be maintained at a pressure less than compressor discharge and bearing the same relation to compressor discharge pressure as does the turbine discharge pressure if the engine is operated with a normal tailpipe having a fixed jet nozzle. Any pressure actuated device such as a pressure switch or transducer can then be connected to the cavity 105 and to the turbine discharge pressure sensing pipe 120 to control any desired operation in response to difference in pressure between these points.

Operation To illustrate operation of the form of the invention thus far described let it be assumed that the afterburner 16 is not in operation and that nozzle 18 is properly set to maintain a normal turbine discharge pressure. Under these conditions the gates 19 and 20 will be fully closed. With a normal turbine discharge pressure the pressure within the pipe 120 will be equal to the pressure in the cavity 105 of the pressure device 1014, and the bellows 115 and 116 will center the contact 126 between the other contacts 124 and 125. Now if the afterburner 16 s...set.,.noperation.thererwillbeafgrearincreaseintern: peratureand .hence involmeffexhaust .gasseeking to. exhaust. throughA the restri'citedanozzle. 18.'. Tliis'.wi1I increase Athe turbinedischarge. pressure abovethe normal value. because otitheA backgpressure. .developedfin the. tail-L pipe.. The increased .pressurelwilllbetransmitted through ther pipe f 120.. to the interior otloellows .1161.' and theA iml creased, pressure. therein V.will ",cause, the movement. fof :the contact .126. to. theleft tm engagecontact ,124,1 closing thev circuittomotor. 13'2...to rotate,itaimafdirectinfto operate,valve 26.. so that,11id,.is.delivered to theright end. of,iluid,motor. 25.. 'Ilhisnseparates or opens. the gates :19; and- 2.0luntil.. the pressure ,.innthe ,tailpipeisref duced. and ,.the. .turbine .dischargepressure againfbecomes normali. When. this...condition.ris.reached. the.. contact 126 will disengagecontact 124,` ,stopping theV motor 132 and 1ocking.,..the hydraulic. motor? lioimthepositionto whicllit was last. .moved.l When., the.; afterburnen oper,.- ation;.is..discontinued the` actionris reversed in...that..con. tact, .126.'. moves, to. engage-contact` 125. with..the result that the .electric and tfluid.. motors 13.2..: and, .25.. operate. -to move the. gates 19 and.20.to closed position..

It. will. be. appreciated by. 4th,o se.skille.d..inthe.art .that the system can beutilized.to.,ca11se.the.variable elements of acontinuously variable-nozzlertobe; continuously adjusted in ,accordance with, uctuating. turbine discharge pressures to keepfthat` pressure at itsrnorrnalvalue.. C011- tinuously variable, nozzles; of., types..v well known.. in theartcan beused-imsuch combination. It.can; also be. utilized, to.. merely shift. thea gates and. 20.- illustratedinFigurel .to..either. fullI opemor; full closedr position. in accordance with the..v larger.. vchanges in.. tailpipe pressure resulting., from.. afterburner.. operation. or dise continuance as explained.. hereinbeforel- Also,.,A instead of. the system. controlling the .nozzle lby. means of. the gates.. 19 and.20,. it..could.beus.ed..to automatically inf creaseor. decreasefthet-supplyco fuel toy theafterburner to maintainA anormal. turbine.. discharge` pressure, in which. event. the. variationin size.4 ofT the. nozzlev 18 re-` quired` when afterburninggis startedo-r.. stopped could be .controlled either by some.A automatic -device or-byhand'. Itcanalso beutilized to. control:` the, turbine.. discharge pressure when water injection is introduced;

Although thee-form. of the. invention'fthus.'fary descnibed provides a sensitive, reliable, fast-acting control system suitableior many applicationsaitv nevertheless has -apracf tical. serviceceiling fof..40,000. feet and is thus` unsuitedfor many. military applications.,

The improvedform :of the. invention. shown. indetail in Figures.y 3 through vSeis completelyunaffected` by` altitude changes` and is. substantially free of mechanical 'resiliency and, consequently, is.the.preferred'form of the invention.

In 'addition-to detailed renementswhich improve: its overall operation, the preferred .formv ofthe invention now. to be describedt'differs from` that previously de.- scribed in two essential respects.. First, thedownstream orifice 110, which, in operation, is; ofA constant areafis replaced by `a variable areaorice, theareaof` which is controlled as a function-off. a differential pressure applied across a pressure' responsive device. Secondly, the bellows units 115 andi-16, whichbecause of' their mechanical resilience orspring rate-*'-introducezerror particularly at high; altitudes; arerreplaced bya relatively largesingle diaphragm' whichhasV mechanical resilience of such low value as compared-tothe applied forces. as to` introduce negligible error Lat-all altitudesin whichjet engines are operational.

Referring now more particularly to Figures 3 through 8 which disclose ythe preferred. embodiment'of the in.- vention in one of its most successful applications, 150 indicates generally a turbo-jet engine generally similar to that shown in Figure 1. The engine has. a compressor 152; a primaryburner 15. 4,`. a .turbine..156,..an

afterburner 158 mounted inatailpipe .1 60 andacontinu:

ously Vvariable area', nozzle` lzjwh'ich may take-Y ang; of

anlumber` of fconventional forms..

The details of .thecontrols for the primary engineand for, the` atferburnenY haveV b'een vomittedlfrom .Figure 3. InClrit-y and."may.b`e ofithe same lgeneral nature...as thbseshown in Figure l or may take other conventional forms.:

The` area of .the. nozzle. 162.n is varied bymovemenhof theshroud "1614 axiallyTv of the engine, movement. toward the right as viewed...in Figuredecreasingthe.sizecof the .nozzle and; movement ,toward -lthe let increasing. thel size of"th`enozzle. Vernier movement iseiected by means .oiayreversible motor 166, thedrive.shaft..168 ofjfwhich moves.. a traveling. nut- .17.0. connected. to the shroud. lilhthrotlglr a..suitable. linkage.. including lever. 172i. Rapid. andjmajor displacements,A ot the nozzleare etfe'ctedf. through-. a.n pneumatic. power mechanism. indie cate.d.. gencrallyl at `1.7.4 ,also connected, to: the.. common lever.. 112% Qperat-ing iluidiorthepower. mechanism 11.4 is bled) from. the.compressor discharge. throughaa conduit 116. and supplriedtselectively tothe.. opposite. .ends ofrthe .powenpistonby lasv-alve 178 vactuatedbysolenoids 18.0 and..132.-. Aetuating; signals .are supplied.- through amplifiers 184 and ..186 ,.to. the.. motor 166 and .the` valve 178,.. respectively, v.by thecont-rol. unitindicated. generally at 190;. with, which` the: present,.invention is..primanily concernedI This.. unit,y Whichreplaceslhe unit.. 104. of Figurefl` and the.associated:. bellows: and. contactmechansnr. is dynamically. connected to.. thejet engine. in,essential1y the same way as the .unit of.Figure, l. Specificallyf thel unit-is..connected...through a conduitf 192 to.vcompressor discharge .and-.through aconduit 19.4. to. the..turbine dis-7 cl1arge:a1'.ea.. Conduitv1196 (rotatedv 909 from its; actualr position). leadsfto any low pressure.. areaofthef aircraft' preferably an area Where..atmospheric pressure prevails.-y

The..unit.190, includesa main body! memberA 200. and, acover, member 2.02,..p referably. of Vdie. cast aluminum, Whichhave: mating. circular anges secured. by... ay plu:l rality of,.screws ,204. Sealingly securedbetween the mat ing tlnges of the members 200 andv 202:.is a circular diaphragm. 206, preferably. fabricated of silicone. laminated liber glass, whichis highlyflexible, durable and substantially nonfresilient'.. Diaphragm, 206-divides the unit; 1.91.0.into anupper. chamber 208. to vwhichthe pres; sure'. tobe, controlled is.- suppliedv through the pipe. 19.4 and'a lower chamber 210 in;whichna reference pressure isestablished'. aswill be..explained` TheY body. member 2.0.0 isprovidedwithftwo secondary chambers 212,.and 214 connected,..respectively, to.the.compressor discharge. pressure. thronghonduit. 19.2 and to ambientA pressure through conduit .196.. The-chambers 212 and.21,4.com1a municate, at..their upper ends with-the referencepressure chamber 21'07through. orifices 216.and 218 formed, respectively, in sheet. metal plates 220 and: 222 which areheld inplace by peeningtheupperedge ofV the charnbers-212;.and, 214. A sheet metal. deflector 224 is-.pro vided. to direct theilow fromorice. 216. toward orifice 218'. to prevent; heat loss. and to minimize turbulence Within-thefdevice. Thedellector-ZzlV is supported byy a die` cast aluminum annulus` 225. and the pressure 'devel-. opedbetween the. orices. 21o-fand 218 is transmitted to. the chamberv 210. through registeringpassages- 226and 228 -formedin the detlector 224 andA the annulusv225.

Securedv to, the lower end of the. body member' 20.0 as by bolts 23.0fis, a secondaryv die .cast aluminumhous-y ing.232 which is closed. by a sheet metal coverP plate 234. An, adjustingv needle 236, by which the area of orice 216- may be adjusted for a purpose to appear, is threaded into housing200. and locked by a Teflon sleeve 238 secured betweenthe housings 200.and 232.-

Rigidly secured to.. the.. diaphragm 206 by any; con: ventional sealing. ,nu t and washer assembly indicated-:at 240 is.a ..nic.kel,plated brassneedle. 242 having laff-tapered control portion 244 preferably having a total taper angle of 6. The tapered portion of the needle is positioned within the orifice 218 throughout the range of movement of the needle 242 permitted by the hollow bosses 246 and 248 formed in the cover plate 202 and the annulus 22S, respectively. The position of the control portion 244 of the needle within orifice 218 and consequently the area of orice 218 is determined by the respective pressures in chambers 208 and 210 acting on opposite sides of the diaphragm 206. Below tapered portion 244, a uniform section of needle 242 extends through a floating seal 250 preferably of Teon clamped between the housings 200 and 232.

The lower end of the needle 242 within housing 232 carries a wiper assembly indicated generally at 260 and illustrated on enlarged scale particularly in Figures 5, 6 and 7. The wiper assembly is supported on the lower end of needle 242 by means of an aluminum sleeve 262 and is held in place by a clip 264 the free ends of which engage an annular recess 266 at the lower end of the needle. Mounted on the sleeve 262 is a rectangular insulating block 268 of silicone ber glass laminate. Wiper contacts 270 and 272 are secured by rivets 274 to the opposite ends of block 268. The wiper 270 rides over the surface of a potentiometer 278 which extends through a silicone ber glass laminate base plate 280 and is threaded into a boss in the housing 232. The position of the potentiometer 278 may be adjusted by the addition or removal of shims 282. The base plate 280, which is also held in place by an additional screw 284 carries a pair of contacts 286 and 288, contact 288 being shown on enlarged scale in Figure 8.

The contact 288 includes a contact post 290 threaded into a self-locking clinch nut 292 mounted on the base plate 280, the clinch nut having a ber friction lock insert 294. Sleeved over the post 290 and held in place between the head of the post and the base of the clinch nut are ber insulating sleeve 296 and a silver contact sleeve 298. The contacts 286 and 288 are identical except that on the contact 288 the position of the sleeves 296 and 298 is reversed. Each of the contacts carries a terminal clip 299.

The wiper contact 272 has two spring arms 300 and 302 which yieldingly ride over the surface of the contacts 286 and 288, respectively. The spring arms may be bent slightly if required to provide uniform contact pressures on the contacts 286 and 288 and the potentiometer 278 thus centering the needle.

Ihe leads from the contactors 286 and 288, from the wipers 270 and 272 and from the potentiometer are connected to a standard connector 310 mounted in the housing 232 and adapted to receive a connector plug 312 leading to the nozzle actuating units.

A typical somewhat simplified wiring diagram applicable particularly to the apparatus of Figure 3 is disclosed in lFigure l0. As there shown the contact Wiper 272 is connected through a lead 316 to a suitable source of potential 318. Accordingly when the needle 242 is moved to its extreme positions into contact with the conducting sleeves of either the contact 286 or the contact 288 a sig-nal is transmitted to the amplifier 186 through one of the leads 320 and 322 thus energizing either one of the coils 180 and 182 through leads 326 and 324 connected to the output side of the amplier, moving the valve 178 to signal full open or full closing of the nozzle depending upon the direction of movement of the needle 242. However, except during initiation or cessation of afterburning, the wiper 272 will be out of contact with the conducting portions of contacts 286 and 288 and Vernier trim of the nozzle will be effected through motor 166 by travel of the wiper 270 over the potentiometer 278 which with its leads 328 and 330 formsl a part of a Wheatstone bridge circuit indicated generally at 332. The wiper 270 is connected directly to amplier 184 through lead 334 and the opposite side of the Wheatstone bridge is connected to the amplifierY through lead 336. The output side of the ampler is connected to` the reversing iields of motor 166 through leads 338 and 340. Accordingly, movement of the contact 270 along the potentiometer from its preset neutral position increases either the voltage applied through lead 334 or lead 336 with respect to the other thus revolving the motor 166 in one direction or the other eecting vernier adjustment of the nozzle position.

The circuit of Figure 10, per se, forms no part of the invention and it will be apparent to those skilled in the art that the illustrated circuit may be replaced by other circuits which will actuate the solenoids 180 and 182 upon full travel of the needle 242 `and will cause motor 166 to revolve in opposite directions upon displacement of the wiper 270 in opposite directions from its neutral position. -It will also be apparent that through the use of conventional circuitry the afterburner fuel and ignition controls can be made operative in response to predetermined movements ofthe needle 242. For simplicity these additional circuits have been omitted from Figure l0.

Figure 9 illustrates a typical circuit for use in controlling a two-position nozzle either with the apparatus of Figure 1 or that of Figure 4 with the potentiometer 278 removed or rendered inoperative. Assuming that the nozzle is fully closed and that afterburning is desired, the main afterburner switch 350 is depressed energizing the fuel valve, not shown, through solenoid 352 and the ignition coil 354 through normally closed relay contacts R2 of relay R. The subsequent increases in tailpipe pressure moves the contact wiper into contact with the conducting portion of sleeve 286 closing holding contacts R1 of relay R and motor closing contacts R3 to open the nozzle. Normally closed contacts R2 are opened thus cutting off the ignition. If the afterburner blows out the resulting decrease in tail pipe pressure moves contact wiper 27 2 into contact with the conducting portion of post 288 energizing relay S opening contacts S1 deenergizing relay R, closing motor operating contacts S3 moving the nozzle toward closed position. Ordinarily, in the absence of inadvertent afterbfurner blowout, the afterburner system is deenergized by opening main afterburner switch 350.

The operation of the entire system of Figures 3 through 8 and l0 will now be described. It will be recalled in connection with the description of the apparatus of Figure l that the areas and relationships of the upstream and downstream oriiices 107 and 110 are such that the pressure ydrop across the orice 107 closely approximates the pressure drop from the discharge side of the compressor through the turbine and the pressure drop across the orice 110 closely approximates the pressure drop through the tailpipe. Essentially the same condition obtains with respect to the apparatus shown in detail in Figure 4. However, in the apparatus of Figure 1 the downstream orifice is essentially xed except for provision for a preflight calibration adjustment whereas the downstream orifice 218 of the apparatus of Figure 4 is continuously varied in operation as a function of the differential pressure between chambers 208 and 210. Consequently under all ight conditions regardless of changes of altitude, ambient temperature, air speed or other er1- vironmental conditions, a reference pressure is established in chamber 210 which simulates a turbine discharge pressure which is at optimum ratio with the prevailing compressor discharge pressure. As long as the turbine -discharge pressure in chamber 208 is exactly equal to the modulating reference pressure in chamber 210 and therefore in optimum ratio with the compressor discharge pressure the diaphragm 206 remains at rest. However, when the pressure in chamber 208 deviates from the established optimum reference pressure in chamber 210 the diaphragm 206 and the needle 242 are moved toward the low pressure area. For example, if the turbine discharge pressure in chamber 208 drops below the referencepressurecinchamber. 210fthe diaphragin'.i 206;- movess upwardly,4 ass. viewed. in `Figure 4; It fthe needle.. 2441were not.- provided With-.the tapered.. control section..

244 l'inf thefregion ofeoxicels. the `displacement of the diaphragm` Wouldconti-nue. until physicallyinterrupted. However, as theV needleis-:displaced .thesize lof oriiice 218 is increased and the reference pressure in chamber..

210 .immediately-dropsand theneedle .comesto restwhen the sizeof the oriiice 218 hasbeen.sufliciently'increased to lower thepressure-inchamber 210.to.the. exact value of thepressure inchamber4 208.V This movement of the needle causes a..corresponding...displacement of. the contact .270 alongathefpotentiometer 278.which, in the casen of a drop--in.turbine discharge pressure, activatesY the.motor-166.through the above-described circuit in a directionto. move :the variable. area nozzle towards closed position.` By design.. the. amount of deflection of the. diaphragm 206and needle .242landthe amount of resulting.V change inthe area.of'the.oriiice.-218 are directly proportionalwto theerror existing in the turbine discharge pressure with. respect to the compressor discharge pres# sureand .thus afford a direct indication of thecorresponding .change in nozzlearea required `to restore the turbine discharge pressure to normal. The diaphragm .andneedle will remain displaced as long Aas error exists in the turbine discharge. pressure. However, .since displacement of the needle produces an immediateA corrective. signal, .in the example given, a nozzle closingsignal, correctioniof theA error in turbine. dischargepressure is initiated immte`V diately upon displacement ofthe needle from 'its-neutral" position. As the nozzle moves toward closed positionand' the turbine discharge pressure returns. to the desired value, the pressurein chamber 208 increasesand becomes greater than the deliberately lowered pressure* in' chamber210 and the diaphragm v2861s accordingly displaced. in a downward direction as'viewed in` Figure 4' which ultimately restores the area of oriiice 218fto 'normal`lr thus stabilizing the. diaphragm inthe original normal posi tion where .the contacter 270"occupies a neutral position` with respect to the potentiometer 278. It will be understood that although the control device returns to its` original position the nozzle will occupy a corrected position.

Inthe case of a temporarily excessive 'turbine-discharge pressure, the diaphragm is displaced inthe downward" direction as viewed in Figure`4 thus restricting the area of orifice 218'and raising the pressure=in chamber 210'.` The diaphragmand needle then come to rest when *the pressures in chambers 208fand 210 are vequal at vvhichv time the displacement of the contact 2.7i) on the potentiometer 278 signals an opening movement olfthe nozzle of the correct magnitude thus restoring the apparatus to itsnormal balanced condition;l Since the correction of turbine discharge' pressure' and theV movement of the diaphragm. 206V and the needle 242 take place simultaneously` and at substantially the same rate, over come pensation, hunting and resilient or pendulum action'are eliminated and the needle has little tendency to lmove past its balanced point.

Ithas` been found in practice that the above-described system will reilect' fluctuations in turbine discharge pressure within .Oil second; This extremely rapid response isy obtained since the unit measures pressure changes directly and avoids time delaysinherentr in an indirect system which utilizesan associatedvaiiable such as temperature. By sensingpressure directly the apparatus of the present invention provides immediate signalsand the .nozzle area is corrected beforeA other variables are seriously effected.

While the above-described functions are predicated on a more or less` minor variation in turbine'discharge pressure,A essentially the same action takes place upon major variations in. turbine discharge pressure such as, for example, thoseoccasioned by afterburner light-ofi or blowout. In. this-l event the diaphragm. is. displaced yrapidly direction desired either-toiullyopen or vfully closedposif,

f. tion. The signal activates the power rnechanismflM-.for

rapidly movingthenozzle and the trimming .actionsignalled. by the.` potentiometer. and. theA motor. 166.is .overriddenu As soon .as .sucientcorrection has takenplace. to` returnthe contact wiper. 272to. the insulated. portions of the `contacts -288 or 286, the*` `final. trimming actionlisF accomplished. through the Aagency of. .the motor 166.-.

Regardless of .the magnitude ofA pressure ,changer and. regardless..of=.the= altitude, air. speed,. r.p.m.y or. ambient temperature the. diaphragm deectionisalways a..func-.. tionofthe error .in nozzlearea and .the diierence between the actual pressure ratio and the desired'normal presa sure `ratio,.since-theoriices andpressure ratios in..thel device 190 exactly. parallel those of the engine. Ifat sea.. level static a.- change of 10%in the. ratiobetwen. turbine disehargepressure and. compressor discharge pressure displaces .thediaphragm suflciently to move the needle. .03.1 inch the-samedisplacement would be causedby a` 1.0% variation in the ratio at altitudes of 60,000.feet or higher. These remarkable results havebeen substan-V tiated by actual test and clearlyestablish-that the apr. paratus of the present invention is inherently self-com@ pensating despite variations inoperating and.. ambient pressure levels.

The controll unitl is calibrated forfra particular. engine. primarily byvarying. the area ofV the orice 216. by the adjustmentof needle.236. This adjustment is madeso` that the Wiper contact 270 occupies the neutral position onthepotentiometer278 when the pressure in the engine tail pipe is normaL Further adjustmentsmay be made by displacement. of `the potentiometer by the addition.or, removalof theshirns 282 orby, reppsitioningythe contacts 28`6"and 288.

As stated above,.it is desirable in a jet engine to render the control unit non-responsive to minor transientvariations in.turbine tail-pipe pressures and accordingly a dead band isordinarily incorporated inthe circuit. This dead band normally renders the unit insensitive to departures of plus or.minus .5% from. the normal tailpipe pressure. Since the control'unit is substantially un. effected by changes in the operating'or ambient pressure. levels, the dead band when4 properly set.at sea level will. remain. constant for allight altitudes.vv Since at ight altitudesadeparture ofplus .or Aminus .5 from the nor.- mal tailpipe pressure will produce the same movement of the wiper along the .potentiometer and thus will, produce a uniform voltage differentialA at all flight altitudes, the dead band may be establishedby renderingpthe amplifier insensitive to a predetermined minimum voltage differential. It will be apparent to. thoseskilled in the art that thedead band mayeasily be. established in .other conventional ways because of. its uniformity at all flight altitudes.

In the preferredembodimentof. the invention the potentiometer278 has a plowerratingvof tive watts and may beutilized Without the amplifier to operate relays, proportional solenoid valves, .magnetic amplifiers or other means of amplification not requiringv thermionic tubes. Wherespace and weight limitations permit theuse of the necessaryV electronic controls, .a variable speed nozzle actuating motormay be used. so thatthe rate of correction eiected .by the motor will be directly proportional to the amount of change required. Essentially the same. result may be obtained through the use of simpler controls by utilizing a constant speed motor which is pulsed to obtain a slower rate of actuation than would result from a continuous motoroperation.

The invention has been thus far described asa control element for a jet engine with an afterburner and vari able area nozzle because it is in such an environment that the unique. advantages of the invention have been most 15 fully and effectively realized at the present time. However, the unique properties of the device also render it suitable for many other widely varying applications such as those shown for example in Figures 11, 12 and 13 which will now be described.

Referring now in detail to Figure ll the present invention is there shown as applied to the control of temperature in a blast furnace where the controls are preferably at a distance from the furnace. The control unit 190 shown schematically in Figure 1l may be identical to that described in detail particularly in connection with Figure 4. Whereas in the embodiment above-described, the control unit 190 is connected in parallel with the jet engine, that is, the duct to be controlled, the control unit in Figure l1 is connected in parallel with a duct system which is independent of the duct to be controlled which in Figure ll is the combustion tube 360 of a blast furnace to which fuel is supplied through a nozzle 362.

The secondary duct system comprises a chamber 364 having a restricted inlet orifice 366 and an outlet orifice 368 the area of which is varied `by a temperature sensitive element 370, `for example, a quartz needle in a metal container, the needle being withdrawn from the orifice 368 upon an increase in temperature in the tube 360. Air or other suitable fiuid, for example, shop air, usually supplied at a pressure from 20 p.s.i.a. to 100 p.s.i.a., is applied to the chambers 210 and 364 from a common inlet 372 through conduit 374. The respective outlet orifices 218 and 368 of the chambers 210 and 364 are connected to ambient pressure through conduits 376 and 378. The pressure developed in chamber 364 is communicated directly to the chamber 208 of the control unit through a substantially unrestricted conduit 380. The contact wiper and the potentiometer 278 of the control unit are connected through a suitable amplifier 381 and conventional circuitry to a reversible motor 382 which actuates a fuel control valve 384.

In operation, when the air supply to the combustion tube 360 varies, assuming a constant fuel flow, there is an immediate temperature change in the tube 360. Assuming that the air flow through duct 360 decreases, producing a temperature increase, the temperature responsive element 370 will increase the effective area of orifice 368 dcreasing the pressure in chamber 364. The decrease in the pressure in chamber 364 is immediately communicated to the chamber 208 and produces downward movement of the needle 242 by an amount which is a function of the temperature change indicated by the unit 370 and consequently a function of the required correction in the rate of fuel flow through nozzle 362. The resulting displacement of the wiper 270 with respect to the potentiometer signals the required decrease in fuel flow. As the fuel flow is decreased the effective area of orifice 368 is also again progressively decreased increasing the pressure in chambers 364 and 208 moving the needle 242 upwardly towards its neutral position and when the temperature in the tube 360 returns to its predetermined normal the system is again in balnace. It will be apparent that an increase in air flow in tube 360, producing a decrease in temperature, will result in an immediate increase in fuel flow to maintain the temperature in tube 360 at its desired level. This system is particularly effective in industrial applications where, as in most cases, a Variable source of air pressure is available since the control is entirely independent of variations in the pressure applied to the system through conduit 372 and also independent of variations between the ratio of the pressures in the supply and exhaust conduits 372 and 378. As pointed out above the unit of the present invention always has the same magnitude of response to a given change in the condition sensed regardless of variations in operating or ambient pressures.

Figures l2 and 13 illustrate the invention as a part of a fiow ratio control system to control the rate of addition of a fluid to maintain a constant .fiow ratio with another fluid fiowing at a variable rate. Such systems have widespread commercial applications as for example for the mixing of paints, fuels or medicines in large quantities, or in a city water fiuorination system where the ratio of fluorine added to the water must be maintained at a constant level regardless of variations in the ow of the water.

Each of the systems of Figures 12 and 13 are suitable for any of these applications. For purposes of illustration the water fiuorination system will be described.

With further reference to Figure l2, 390 indicates a city water main having a flow chamber 391 between upstream and downstream orifices 392 and 394. The chamber 391 is in direct communication with chamber 208 of the control unit through an unrestricted conduit 396 and the reference pressure chamber 210 of the control unit is connected in parallel with the chamber 391 through inlet and outlet conduits 398 and 400. Fluorine is added to the chamber 391 through a conduit 402 at a rate determined by the setting of valve 404 which is controlled by a motor 406 in response to signals from the control amplifier 408. The apparatus of Figure 12 is preset so that the desired ratio of fluorine and water owing through orifice 394 is maintained when the contact wiper 270 occupies its neutral position on the potentiometer 278. If the water supply pressure falls, the pressure in chambers 391 and 208 will exceed the reference pressure in chamber 210 because of the excessive flow of fiuorine. Accordingly, the needle 2.42 will be urged into the orifice 218 and its displacement Will be continued until the pressure in chamber 210 equals the pressure in chambers 391 and 208. The corresponding movement of the contact wiper 270 on the potentiometer 278 will produce a control signal to actuate the Valve 404 to decrease the flow of fiuorine decreasing the pressure in chambers 391 and 208 causing the system to return to its neutral position at which time the fiowratio is again established at the desired value. If the fiow of iiuorine decreases with respect to the water fiow through the main 390 the reference pressure in chamber 210 will exceed the pressure in chambers 208 and 391, the needle 242 will be Withdrawn from the orifice 218 until the pressures in chambers 208 and 210 are equalized and the required correction of the setting of valve 404 is made. Again the apparatus of the present invention is of particular utility because it functions to maintain the desired flow ratio regardless of variations in the water main pressure or fiow rate. The system of Figure 13 is similar to that of Figure 12 except that the control pressure is developed in a conduit system independent of the water main.

With continuing reference to Figure 13 the water main 410 is provided with a single restriction 412, and a control chamber 414 having entrance and exit orifices 416 and 418 respectively, is connected to the Water main at points upstream and downstream of restriction 412 through conduits 420 and 422, respectively. The chamber 414 is in communication with the chamber 208 of the control unit through an unrestricted conduit 424 and the chamber 210 of the control unit is arranged in parallel with the chamber 414 by means of conduits 426 and 428. Fluorine is supplied to the chamber 414 through a conduit 430 at a rate determined by the setting of valve 432 in turn controlled by a motor 434 activated by the control amplifier 436.

If the pressure in the main 410 decreases, the pressure in chamber 210 decreases with respect to the chambers 208 and 414 because of the excessive flow of fiuorine and the corrective action is effected in exactly the same manner as that described in connection with Figure 12 to establish the desired flow ratio.

While the invention has been described in connection with three of its major applications it is to be understood that these examples are Vgiven by way of illustranon only and that the present invention has many other commrial and military applications where close regulation of fluid flow systems is required. For example the invention can be utilized to control both a variable area nozzle and afterburner fuel supply in a jet engine or it may be used to control stationary turbine power plants in a variety of ways. It is also adaptable to the control of pressurizing systems, air conditioning systems, wind tunnels, turbo-supercharging systems and similar systems.

In addition to its utilization as a control it may also provide a reliable indicating apparatus. For example, in the apparatus of Figure 11 it was pointed out that the displacement of the needle 242 is directly proportional to the variation in temperature. Accordingly through the use of conventional mechanisms the displacement of the needle can be used to indicate temperature directly. Similarly in the major embodiment of the present invention the displacement of the needle is proportional to pressure variations and accordingly the invention may provide a direct pressure reading through the use of conventional mechanisms. The units herein disclosed may also be used as a Mach meter.

In all of its application the desired results are obtained from the use of the basic combination including a first duct, a second duct which is an analog of the first duct, means having substantially no mechanical resilience responsive to pressure differentials between said ducts and means responsive to the pressure sensitive means to provide a direct indication of a condition in the first duct or to control one of the conditions in the first duct.

The invention may be embodied in other specific forms without departing from the spirit or essentialcharacteristics thereof.L The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated bythe appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. In a gaseous turbine power plant including a compressor, a control assembly comprising a chamber having an inlet orifice connected to be subject to the compressor discharge pressure and an outlet orifice connecting said chamber to a pressure below the turbine discharge pressure, a movable pressure responsive device connected to the subject tothe pressure in said chamber and yto the turbine discharge pressure, a control element movable with said pressure responsive device and extending through one of said orifices to vary the area of one of said orifices upon displacement of said pressure responsive member, the effective area and configuration of said orifices being so related when said pressure responsive device is in its neutral position as to establish in said flow chamber a pressure substantially equal to the normal turbine discharge pressure, and means responsive to displacement of said pressure responsive device when said turbine discharge pressure departs from its normal value for restoring said turbine discharge pressure to its normal value.

2. Apparatus for indicating variations from normal of the turbine discharge pressure of a gaseous turbine power plant having a compressor, comprising a chamber having an inlet orifice connected to be subject to the air compressor discharge pressure and an outlet orifice connecting said chamber and a pressure below said turbine discharge pressure, a movable pressure responsive device connected to be subject to the pressure yin said chamber and to said turbine discharge pressure, a control element movable with said pressure responsive device and extending through one of said orifices to vary the area of one of said orifices upon displacement of said pressure responsive device, the effective area and configuration of said orifices being so related when said pressure responsive device is in its neutral position as to establish in said 18 ow chamber a pressureI substantially equal to said normal turbine discharge pressure, whereby a displacement of said pressure responsive device from its neutral position is indicative of a departure of said turbine discharge pressure from its normal value. l Y

3. In a fluid operated mechanism having a flow vof fluid through a main chamber under variablepressure, said main chamber having a restricted entrance and exit, lan auxiliary flow chamber having an inlet orifice and an outlet orifice, means connecting the entrance of said main chamber and said inlet orifice with a common fluid pressure source, the exit of said main chamber and said outlet orifice exhausting to a pressure lower than the pressure in said main chamber, a movable pressure responsive device connected to be subject to the pressure in said cham-'- bers, a control element movable with said pressure responsive device and extending through one of said orifices to vary the area of one of said orifices upon displacement of said pressure responsive device, the effective area and configuration of said orifices being so related when said pressure responsive device is in its neutral position as to establish in said ow chamber a pressure substantially equal to a desired pressure in said main chamber, and operating control means responsive to movement of said pressure responsive device when the pressure in said main chamber departs from said desired value to vary the restricted exit of said main chamber for restoring the pressure in said main chamber to its desired value.

v 4. A fluid pressure operated mechanism having a flow of fluid through a main chamber under variable pressure, said main chamber having a restricted entrance and exit formed respectively by entrance and exit orifices; means forming an auxiliary flow chamber having a restricted entrance and exit formed respectively by entrance and exit orifices; means connecting the entrance of each of said chambers with a common fluid pressure source, the exit of each of said chambers exhausting to a pressure below the pressure in said main chamber, a movable pressure responsive device connected to said chambers and normally occupying a neutral position and movable away from said neutral position in response to differential pressures between said chambers; a control element movable with said pressure responsive device and extending through one of said orifices to vary the area of one of said orifices upon displacement of said pressure responsive device, the effective area and configuration of said orifices being so related when said pressure responsive device is in its neutral position as to establish in said flow chamber a pressure in constant ratio to the pressure at said common source, and means responsive to displacement of said element away from said neutral position to generate a signal when a differential pressure exists between said chambers.

5. ln a variable pressure system comprising a first pressure zone and a second pressure zone, a device for measuring changes in ratio between the pressure in the first and second pressure zones, said device comprising a chamber, a freely movable pressure responsive device dividing said chamber into two compartments, a restricted inlet orifice in one compartment connected to the first pressure zone and a restricted outlet orifice in said one compartment leading to a pressure below the pressure in said one compartment, an inlet in the other compartment connected to the second pressure zone, said pressure responsive device being subjected to the pressures in both compartments, an orifice control member connected with the pressure responsive device land extending through one of said orifices to vary the area of the orifice upon displacement of the pressure responsive device thereby to bring the pressure in said one compartment into balance with the pressure in the other compartment, the effective area and configuration of the orifices and orifice control member being such that the pressure responsive device is in its neutral position when the ratio of the pressures in the pressure zones has a predetermined normal value.

6. The system as defined in claim together with operating control means responsive to movement of the orifice control member when the pressure responsive device is moved from its neutral position to restore the ratio of the pressures in the first and second pressure zones to said normal value.

7. In a turbine engine having an air compressor, a turbine, and regulating means for varying the turbine discharge pressure, apparatus for maintaining the ratio between the compressor discharge pressure and turbine discharge pressure at a predetermined normal value comprising a chamber, a pressure responsive device dividing said chamber into two compartments, a restricted uid inlet orifice in one compartment connected with the compressor discharge pressure and a restricted fluid outlet orifice in said one compartment leading to a pressure below said turbine discharge pressure, an inlet in the other compartment connected with the turbine discharge pressure, said pressure responsive device being subjected to the pressures in both compartments and being freely movable in response to changes therein, an orifice control member connected with the pressure responsive device and extending through one of said orifices to vary the area of the orifice upon displacement of the pressure responsive device thereby to bring the pressure in the said one compartment into balance with the pressure in the other compartment, the effective area and configuration of the orifices and the orifice control member being such that the pressure responsive device is in its neutral position when the ratio of the compressor discharge pressure to the turbine discharge pressure has said predetermined normal value, and operating control means responsive to movement of the orifice control member when the pressure responsive device is moved from its neutral position to restore the ratio of the compressor discharge pressure to the turbine discharge pressure to said normal value.

8. In a turbojet engine having an afterburner and a fully variable nozzle through which the propulsive gases flow, and an actuator for said nozzle; apparatus for maintaining the ratio between the compressor discharge press'ure and turbine discharge pressure at a predetermined normal value under al1 operating conditions comprising a chamber, a -freely movable pressure responsive device dividing said chamber into two compartments, a re'- stricted fluid inlet orifice' in one compartment connected with the compressor discharge pressure andY a restricted fluid outlet orifice in said one compartment leading vto a pressure below said turbine discharge pressure, an inlet in the other compartment connected with the turbinedischarge pressure, said pressure responsive device being subjected to the pressures in both compartments and being freely movable in response to changes therein, an orifice control member connected with the pressure responsive device and extending through one of said orifices to vary the area of said one orifice upon displacement of the pressure responsive device thereby to bring the pressure in said one compartment into balance with the pres-y sure in the other compartment, the effective area and configuration of the orifices and the orifice control member being such that the pressure responsive device is in its neutral position when theA ratio of the compressor discharge pressure to the turbine discharge pressure has said predetermined normal value, and operating control means responsive to movement of said pressure responsive device away from its neutral position to operate said nozzle actuator to move said nozzle to restore the ratio of the compressor discharge pressure to the turbine discharge pressure to said normal value.

References Cited in the le of this patent UNITED STATES PATENTS 436,235 Grin Sept. 9, 1890 2,082,940 Brisbane et a1. June 8, 1937 2,312,880 Coffeel Mar. 2, 1943 NOlV. 9, 2,580,962 Sedille Jan. l, 1952 2,600,073 Plank June 10, 1952 2,623,352 Sedille et al. Dec. 30, 1952 2,649,108 Best et al. Aug. 18, 1953 2,632,474 Jones Mar. 24, 1953 2,641,324 Fortescue June 9, 1953 2,677,233 Iordan May 4, 1954 2,746,242 Reed May 22, 1956 FOREIGN PATENTS 278,689 Germany Oct. 2, 1914 636,879 Germany Oct. 19, 1936 634,095 Great Britain Mar. 15, 1950 

